Method of making high-strength bleach.



UNITED STATES PATENT onnion.

KARL P. MOELROY, OF WASHINGTON, DISTRICT OF COLUMBIA.

METHOD OF MAKING HIGH-STRENGTH BLEACH.

No Drawing.

T 0 all whom it may concern:

Be it, known that I, KARL P. MoELRoY, a citizen of the United States, residing at Washington, in the District of Columbia, have invented certain new and useful Improvements in Methods of Making High- Strength Bleach, of which the following is a specification.

This invention ,relates to methods of making high strength bleach; and it comprises a process of making bleaching preparations, such as hypochlorite of calcium,

hypochlorite of sodium, etc., containing but small proportions of chlorids, or substan- ,tially none wherein chlorin is treated with steam (water vapor) or water at or near the boiling point under circumstances favoring condensation or retention of HCl formed by hydrolysis therewith and the remaining vapors are led into contact with a base, such as caustic soda or lime, to form a hypochlorite; all as more fully hereinafter set forth and as claimed.

'hile the exactchemical nature of the various preparations made by passing chlorin into contact with a base, such as lime, caustic soda, caustic potash, etc., is still more or less a debatable matter, for the present purposes they may be considered as a physical mixture of a chlorid and a hypochlorite; ordinary bleaching powder for example being a mixture of calcium chlorid and calcium hypochlorite. As ordinarily represented in the usual formal equation, (which may be here used as representing the actions occurring) the chlorin reacts with water in the following sense:

Presuming caustic soda to be the alkali. the hydrochloric and hypochlorous acids -nnite with it to form sodium chlorid XaCl and sodium hypochlorite, XaClO.

The bleaching or oxidizing power of such a preparation is the same as that of the oxygen of the hypochlorite which tendsto lose 0 and become XaCl. Since 0 is equal to C1 it is the same as that. of the chlorin used.

For the present purposes the oxidizing power of the chlorin (C1 used may be said to be concentrated in one of the products of reaction, the other (the XaCl) being inert.

In the usual methods of making these bleaching preparations. chlorin is simply passed over moist lime by which it is ab- Specification of Letters Patent.

Application filed August 30. 1917.

Patented Apr. 2, 1918.

Serial No. 188,953.

sol-bed with developmentof some heat and formation of the ordinary bleaching powder, which. as stated, may be here regarded as a mixture of the two salts. Liquid bleaching preparations are made with caustic soda solution and caustic potash solu tion by simply passing chlorin into a solution of the alkali. In all these methods the presence of the chlorid has been regarded as inevitable there being no connnercial way of making the hypochlorite alone; that is of making a hypochlorite without also making an equivalent amount of a chlorid. 'lhe desirability of making a preparation which will contain only hypochlorite however is obvious since it has. much more bleaching power than 'a mixture containing chlorid only. For example, a pure molecular mixture of sodium chlorid and hypochlorite such as may be represented by the symbols XaCl and XaClO, carries about 12 per cent of available oxygen; an amount which however is not reached in practice. The hypochlorite alone on the other hand would carry about :21 per cent. of available oxygen.

I have found that I can make bleaching prc mrations in which the ratio of hypochlorite to chlorid is much liighelzythan the usual 1 1 molecular ratio strivcn for in the usual bleaching preparations. This I do by taking advantage of the dill'crent volatility or vapor tensions. of the two acids in the presence of water at 100 C. or thereabout. In the presence of sutficicnt water at a high tcmperture the HCl may be held back in solution. or substantially so. while the H(l() volatilizcs or remains in the vapor form. In practice. I may simply mix chlorin and steam at about the condensing point of water. that is at about 10)" t. and provide means whereby the condensing water takes down with it the Htl formed in the rcaction while the ll(l(,) vapors are not so condensed but pass forward. It is not necessary to use .-tcamboiling water may be. used instead. I may for example pass chlorin upward through an apparatus like the usual column stills against a down coming clrrcnt of hot water and in the presence of water vapor. Under these conditions the chlorin probably reacts with the water or water vapor to form llCl and HClO. the former remaining dissolved "in the hot water while the latter passes forward in the vapor form. The outlet from the still is connected to one or more receivers carrying caustic alkali of some kind; this alkali being "either lime or causticsoda according to the hypochlorite desired. The vapors must be thoroughly cooled atthe time of contactwvith the alkali to prevent undesired side reactions. Instead of preforming chlorin and mixing it with steam, or hot Water, I may take the hot moist mixture of water vapor and chlorin coming from an electrolytic cell electrolyzing salt and introduce this mixture into a still-like reaction chamber, thereby economizing in theamount of steam to be supplied or doing away with it altogether as the case may be. In another variant of my invention instead of forming chlorin as such I simply run an electrolytic soda cell at a hightemperature and with plenty of vapor space above the electrolyte. Under these conditions the chlorin as it forms hydrolyses with the water or water vapor and forms HGl which goes into solution in the condensing water and is returned to the electrolyte for re-electrolysis. The HClO formed passes forward out of the cell together with steam or water vapor. The mixture is caught in caustic alkali, as before. I

In the methods described I usually obtain solutions of hypochlorite' containing a cons derable amount of water formed by the condensation of the steam or water vapor going forward with the HCl('). These solutions I simply evaporate to crystallization or dr \ness, using as low a temperature as practicable and under vacuum conditions. In order to avoid side reactions leading to a loss of bleaching power it is in general better to have the condensed liquid as nearly neutral as possible before any heating in evaporation; that is to pass in HCl() vapors until the soda or lime, as the case may be,

2. The method of making a strongbleaching preparation which comprises reacting upon H O with C1 at a temperature around (7., and passing the vapors into contact with caustic alkali.

In testimony whereof, I affix my signature.

K. P. MGELROY.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. 0. 

